This is a proposal to study DSM-III hypochondriasis in general medical patients. There are five aims: (1) To clarify the nosologic status of hypochondriasis; (2) To examine the boundaries between hypochondriasis and other psychiatric disorders that have hypochondriacal features; (3) To examine the relationship between hypochondriacal symptoms and serious medical disease; (4) To study the utilization of medical care services by hypochondriacs; (5) To explore primary care physicians' difficulties in caring for hypochondriacal patients. Hypochondriasis is an important and prevalent problem in general medicine, but it is largely unexplored because it is infrequently seen in psychiatric settings. It is not only a source of chronic suffering and disability to the patient, but of frustration in the physician. Hypochondriasis is also a very costly public health problem because it results in over-utilizaiton of medical services (repeated physician visits, duplication of laboratory tests) without improvement of the patient's symptoms. Effective treatment awaits greater knowledge of the condition and this study is therefore envisioned as the first in a sequence of studies that will lead to controlled intervention trials. A sample of 100 hypochondriacal patients will be identified by screening a general outpatient medicine clinic and will be compared with a random sample of 100 patients from the same setting. Patients will be studied with structured and semi-structured interviews, self-report questionnaires, and tests of somatic perception. Their medical records will be reviewed, and their primary physicians will complete a structured questionnaire. We will measure hypochondriacal symptoms (based upon the DSM-III definition), utilization of medical care, other DSN-III psychiatric disorder, medical status, disability, perceptual style, and physicians' views of their patients. Using these data, hypochondriacs will be compared to non-hypochondriacs in order and medical disorder, and explore its impact upon the medical care process. The study will investigate some etiologic factors with therapeutic implications, including the tendency to amplify somatic sensation and the cognitive attribution process. The results of this work will lead to earlier identification of hypochondriacal patients, to imporved medical management, and to more specific therapies.